Heating device for copying machines

ABSTRACT

In a heating device for a copying machine comprising a conveyor for continuously conveying a copying paper and an electric heater for heating the copying paper a rotatable body is arranged to be rotated by the movement of the copying paper and means responsive to the rotation of the rotatable body for deenergizes the electric heater when the speed of the copying paper decreases to a value less than a predetermined value.

United States Patent Furuichi et al.

[451 Oct. 10,1972

HEATING DEVICE FOR COPYING MACHINES Inventors: Masayoshi Furuichi; Takaaki Konuma, both of Tokyo-to, Japan Katsuragawa Denki Kabushiki Kaisha, Tokyo-to, Japan Filed: June 29, 1971 Appl. N0.: 157,990

Assignee:

Foreign Application Priority Data June 30, 1970 Japan ..45/57066 US. Cl. ..219/216, 34/], 34/48,

118/5, 219/388, 250/65 ZE, 263/6 E Int. Cl. ..H05b 3/00 Field of Search ..219/216, 388; 263/6 E;

250/65 ZE, 65 T; '34/1, 48; 1l7/17.5; 118/5, 620, 637, 641-643 References Cited UNITED STATES PATENTS 3,444,354 5/1969 Mindell ..219/216 3,452,181 6/1969 Stryjewski ..219/388 X Primary ExaminerC. L. Albritton AttorneyBoswor th, Sessions, Herrstrom & Cain 5 7] ABSTRACT ln a heating device for a copying machine comprising a conveyor for continuously conveying a copying paper and an electric heater for heating the copying paper a rotatable body is arranged to be rotated by the movement of the copying paper and means responsive to the rotation of the rotatable body for deenergizes the electric heater when the speed of the copying paper decreases to a value less than a predetermined value.

4 Claims, 2 Drawing Figures 1 HEATING DEVICE FOR COPYING MACHINES BACKGROUND OF THE INVENTION This invention relates to a heating or drying device for a copying machine and more particularly to a safety device for the heating device which prevents burning of the drying device.

In an electrophotographic copying machine a copying or recording paper on which a powder image has SUMMARY OF THE INVENTION It is an object of this invention to provide an improved heating device for a copying machine including a safety device which can prevent overheating and/or burning of a copying paper in case of a fault.

Another object of this invention is to provide an improved safety device of simple construction which in response to a decrease in speed of a copying paper automatically deenergizes the electric heater of the heating device.

Still another object of this invention is to provide an improved heating device for :1 copying machine which is economical in operation and can positively prevent burning of the copying paper.

According to this invention there is provided a heating device for a copying machine of the type comprising conveyor means for continuously conveying a copying paper and an electric heating element for heating the copying paper while it is being conveyed characterized in a rotatable body arranged to be rotated by the movement of the copying paper and means responsive to the rotation of the rotatable body for deenergizing the electric heating element when the speed of the copying paper decreases to a value less than a predetermined value.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing:

FIG. 1 shows a perspective view, partly broken away, of a heating device provided with a safety device embodying the invention; and

FIG. 2 shows a schematic diagram of the safety device.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference now to FIG. 1, the heating or drying device shown therein comprises a plurality of transverse electric heating elements mounted below a cover plate 11, and a plurality of conveyor belts 12 passing around guide rollers 13 and movable in the direction of the arrow by a suitable drive, not shown. At the entrance end of the drying device, that is, upstream of heating elements 10, there is provided an operating lever 14 of a switch 8, (see FIG. 2) along with one or more discs 15 for detecting the movement of the copying paper (not shown). As shown, discs 15 are positioned close to the heating elements 10. Lever 14 and discs 15 are constructed such that they will not interfere with the movement of the paper. As the paper is entered into the heating device it first depresses lever 14 to close switch S The paper then causes disc 15 to rotate, which in turn rotates a disc 16 having a plurality of perforations 17 around its periphery. The disc 16 may be coupled with discs 15 directly or through a belt or gears, not shown. A source of light 18 (FIG. 2) is located on one side of disc 16 to project light through the perforations 17 to a photoelectric detector element such as a phototransistor 19 to produce electric pulses at a rate corresponding to the rate of rotation of the perforated disc 17. This arrangement detects that the paper is advancing at a predetermined speed by detecting the integrated value of the pulse, in a unit time interval.

In such a heating device it is usual to arrange the conveyor belts 12 to run on the upper surface of a suction box 20 having a perforated upper side so as to draw the paper against the conveyor belts in order to prevent the paper from coming into contact with the heating elements. Lever l4 and discs 15 are disposed to project through openings in the upper side of box 20 to be operated by the copying paper. Should the suction system of the suction box or the driving system of the conveyor belts fail it becomes impossible to continuously advance the paper with the result that the paper will remain for long periods beneath the heating elements. With the novel safety device, however, when the progress of the paper is stopped the rotation of the rotary discs is also stopped to operate the paper running detection circuit for interrupting the circuit of the heating element.

FIG. 2 shows one example of the connection of the detection circuit. The output pulse produced by phototransistor 19 is applied to the base electrode of a transistor 21 through a DC blocking capacitor C a diode D and a resistor R The collector electrode of phototransistor 19 is connected to one pole of a DC source in the form of a full wave rectifier 22 energized from an AC source (not shown) through line 23 and a transformer 24. A capacitor C is connected across the output of diode D and discharge resistors R and R are connected across capacitor C via-a reverse current blocking diode D In parallel with capacitor C is connected a discharge resistor R, which cooperates with resistor R to form a potentiometer. A relay coil RL is connected in series with the collector electrode of transistor 20 and a resistor R and a smoothing capacitor C are connected across the output terminals of rectifier 22. A relay coil RL is connected in series with switch S, operated by lever 14 across lines 23 to the AC source. Heating elements 10 are connected across lines 23 through serially connected contacts S and S and a contact S interlocked with contact S is connected across serially connected contacts S and 8,. Contacts S and 8;, are operated by relay RL whereas contact 8., is operated by relay RL as shown by the dotted lines.

During the normal operation of the copying machine, heating elements 10 are initially connected across lines 23 through normally closed contact S and as a copying paper which has been transfer printed or developed enters the heating device it depresses lever 14 to close switch 8,, thus closing contact S and opening contact S Disc 15 is rotated immediately after the operation of switch 8 so that the perforated disc 16 is rotated and capacitor C is charged with the output pulses produced by the phototransistor 19. The terminal voltage of capacitor C is proportional to the pulse rate or the integrated value thereof. When the terminal voltage of capacitor C reaches a predetermined value, transistor 21 becomes conductive to energize relay coil RL thus closing contact S Closure of contact 8,, reenergizes heating elements 10. Since heating elements are deenergized for only a very short time, the temperature thereof does not vary appreciable and does not affect the operation of the drying device. When the trailing endof the paper has passed over lever 14, switch S is opened to deenergize relay RL thus closing contact 8;, and opening contact S Should the movement of the paper be stopped because, for example, of the failure of the evacuation system connected to suction box 20 or of the driving system for the conveyor belts, the rotation of discs and hence perforated disc 16 is stopped so that phototransistor 19 stops the generation of pulses. Capacitor C is then rapidly discharged through resistor R to render transistor 21 nonconductive. Thus, relay coil RL is deenergized to open contact 8., to disconnect heating elements 10 from source 23. In this manner, overheating and/or burning of the paper is positively prevented.

Thus, it will be clear that the invention provides a new safety device for a heating device of a copying machine by which overheating or burning of the copying paper can be prevented. Utilization of the photoelectric detector greatly decreases the load imposed thereby upon the recording paper.

lt should be understood that the invention can be modified in various ways within the scope of the invention. For example, any photoelectric transducer such as a CdS element may be substituted for the phototransistor 19. Further, it will be clear that two or more detector discs 15 and levers 14 may be used for treating papers of various width.

We claim:

1, In a heating device for a copying machine of the type comprising conveyor means for continuously conveying a copying paper and an electric heating element for heating said copying paper while it is being conveyed by said conveyor means, the improvement which comprises a rotatable body arranged to be rotated by the movement of said copying paper and means responsive to the rotation of said rotatable body for deenergizing said electric heating element when the speed of said copying paper decreases to a value less than a predetermined value.

2. The heating device according to claim 1 which further includes a perforated disc driven by said rotatable body, a source of light positioned on one side of said disc, a photoelectric transducer disposed on the opposite side of said disc for producing an electric pulse, and means responsive to the number of pulses produced in a predetermined interval for controlling the energization of said electric heating element.

3. The heating device according to claim 1 which further includes a switch disposed before said rotary body and arranged to be operated by said copying paper for energizing said heating element.

4. The heating device according to claim 1 which further comprises a suction box having a perforated top side and wherein said conveyor means 18 disposed to slide along said perforated top side and said rotary body projects upwardly through said top side to be contacted by said copying paper. 

1. In a heating device for a copying machine of the type comprising conveyor means for continuously conveying a copying paper and an electric heating element for heating said copying paper while it is being conveyed by said conveyor means, the improvement which comprises a rotatable body arranged to be rotated by the movement of said copying paper and means responsive to the rotation of said rotatable body for deenergizing said electric heating element when the speed of said copying paper decreases to a value less than a predetermined value.
 2. The heating device according to claim 1 which further includes a perforated disc driven by said rotatable body, a source of light positioned on one side of said disc, a photoelectric transducer disposed on the opposite side of said disc for producing an electric pulse, and means responsive to the number of pulses produced in a predetermined interval for controlling the energization of said electric heating element.
 3. The heating device according to claim 1 which further includes a switch disposed before said rotary body and arranged to be operated by said copying paper for energizing said heating element.
 4. The heating device according to claim 1 which further comprises a suction box having a perforated top side and wherein said conveyor means is disposed to slide along said perforated top side and said rotary body projects upwardly through said top side to be contacted by said copying paper. 